Quantum dot digital radiographic detection system

ABSTRACT

A digital quantum dot radiographic detection system described herein includes: a scintillation subsystem and a semiconductor visible light detection subsystem (including a plurality of quantum dot image sensors). In a first preferred digital quantum dot radiographic detection system, the plurality of quantum dot image sensors is in substantially direct contact with the scintillation subsystem. In a second preferred digital quantum dot radiographic detection system, the scintillation subsystem has a plurality of discrete scintillation packets, at least one of the discrete scintillation packets communicating with at least one of the quantum dot image sensors.

The present application is an application claiming the benefit of U.S.Provisional Patent Application Ser. No. 61/364,448, filed Jul. 15, 2010.The present application is based on and claims priority from thisapplication, the disclosure of which is hereby expressly incorporatedherein by reference in its entirety.

BACKGROUND OF INVENTION

Disclosed herein is a digital radiographic detection system and, morespecifically, a quantum dot digital radiographic detection system.

Digital radiography (“DR” or “DX”) is a form of X-ray imaging, where asemiconductor visible light detection device (e.g. digital X-ray sensorsor imagers) is used instead of traditional photographic film. Thesemiconductor visible light detection device is used to record the X-rayimage and make it available as a digital file that can be presented forinterpretation and saved as part of a patient's medical record. U.S.Pat. No. 7,294,847 to Imai, U.S. Pat. No. 7,250,608 to Ozeki, and U.S.Pat. No. 5,017,782 to Nelson describe examples of digital radiographicdetection devices (also referred to as “radiographic detectors”) andrelated technology and are herein incorporated by reference. Thedisclosures of these references are herein incorporated by reference.

Advantages of digital radiography over traditional photographic filminclude, but are not limited to, the fact that digital radiography hasthe ability to digitally transfer images, the ability to digitally saveimages, the ability to digitally enhance images (e.g. the ability toapply special image processing techniques that enhance overall displayof the image), the ability to use images that might otherwise have beeninsufficient (e.g. a wider dynamic range makes digital radiography moreforgiving for over- and under-exposure), the ability to immediately havean image available for preview (e.g. time efficiency through bypassingchemical processing), the ability to use less radiation to produce animage of similar contrast to conventional radiography, and the abilityto reduce costs (e.g. costs associated with processing film, managingfilm, and storing film).

Conventional digital radiographic detection devices (also referred to as“silicon-based light detection devices”) currently use digital imagecapture technologies such as CCD (charge coupled device) and CMOS(complementary metal oxide semiconductor) image sensors (also referredto as “semiconductor visible light detectors” or “imagers”) as theunderlying semiconductor technologies. Both CCD and CMOS image sensorsare silicon-based image sensors that require overlying scintillationlayers for indirect conversion of X-rays into visible light. Both CCDand CMOS image sensors use light detectors to read the overlyingscintillation layer. Both types of image sensors convert light intoelectric charge and process it into electronic signals. In a CCD imagesensor, every pixel's charge is transferred through a very limitednumber of output nodes (often just one output node) to be converted tovoltage, buffered, and sent off-chip as an analog signal. Because all ofthe pixels in the CCD sensor can be devoted to light capture, the CCDsensor has a high output uniformity (which generally results in betterimage quality). In a CMOS image sensor, each pixel has its owncharge-to-voltage conversion so the CMOS image sensor has lower outputuniformity than the output of the CCD image sensor. On the other hand,the CMOS image sensor can be built to require less off-chip circuitryfor basic operation. The CMOS image sensor also includes additionalfunctions such as amplifiers, noise-correction, and digitizationcircuits so that the CMOS image sensor chip outputs digital bits.

Conventional silicon-based image sensors (including CCD and CMOS) havebeen used for indirect conversion of ionizing X-radiation into visibleimages for medical and dental use. There are, however, inherent physicaldrawbacks to the use of CCD and CMOS sensors for X-radiographyincluding, but not limited to the requirement of relatively thickscintillation layers, the requirement that detectors must be embeddedwithin the physical body of the silicon device, the requirement of largeindividual detector sizes, low detector efficiency for capturinggenerated photons, low active sensor detection area/total detector sizeratio, the inability to optimize peak sensor optical sensitivity to thescintillation chemistry, and the narrow practical dynamic range betweenover and under exposure by practitioner. These limitations result in ablurred image, low sensor image contrast, and a narrow dynamic range. Awide variety of techniques, including unique physical designs of thescintillation layer and software compensations, are required to minimizethese limitations.

From a practitioner's perspective, direct digital radiographic detectiondevices that use CCD and CMOS image sensors have diagnostic qualitiesthat are very poor as compared to direct digital radiographic detectiondevices that use traditional film. Digital radiographic detectiondevices that use CCD and CMOS image sensors have poor edge definition inthe native image, poor contrast levels in the native image, very narrowdynamic range between over and under exposed images, and most of thephotons generated by the scintillation layer (over 95%) are simply notdetected. Without significant software enhancement CCD and CMOS imageswould not be diagnostic. The limitations are inherent to how CCD andCMOS image sensors function.

A quantum dot (fluorescent semiconductor nanocrystal) is a semiconductorwhose excitations are confined in all three spatial dimensions. As aresult, the quantum dots have properties that are between those of bulksemiconductors and those of discrete molecules. Simplistically, quantumdot detectors are semiconductors whose conducting characteristics areclosely related to the size and shape of the individual crystal.Generally, the smaller the size of the crystal, the larger the band gap,the greater the difference in energy between the highest valence bandand the lowest conduction band becomes, therefore more energy is neededto excite the dot, and concurrently, more energy is released when thecrystal returns to its resting state. One of main advantages in usingquantum dots is that because of the high level of control possible overthe size of the crystals produced, it is possible to have very precisecontrol over the conductive properties of the material and fine tune thepeak sensitivity to the frequency being detected.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein is a digital radiographic detection system and, morespecifically, a quantum dot digital radiographic detection system.

A first preferred digital quantum dot radiographic detection systemdescribed herein includes: a scintillation subsystem and a semiconductorvisible light detection subsystem. The scintillation subsystem convertsX-ray ionizing radiation into luminescent visible light. Thesemiconductor visible light detection subsystem has a quantum dotsemiconductor substrate and a plurality of quantum dot image sensors.The quantum dot image sensors detect the visible light from thescintillation subsystem and convert the visible light into at least oneelectronic signal. The plurality of quantum dot image sensors is insubstantially direct contact with the scintillation subsystem. A firstpreferred digital quantum dot radiographic detection system mayoptionally have one or more of the following inventive features: theplurality of quantum dot image sensors being arranged in an array; theplurality of quantum dot image sensors being heterogeneous; thescintillation subsystem including a plurality of discrete scintillationpackets (which may be heterogeneous), at least one of the discretescintillation packets communicating with at least one of the quantum dotimage sensors; an optically opaque layer being positioned betweendiscrete scintillation packets; an optically opaque lateral layer withoptical retroflectors positioned opposite the quantum dot image sensors.

A second preferred digital quantum dot radiographic detection systemdescribed herein includes: a scintillation subsystem and a semiconductorvisible light detection subsystem. The scintillation subsystem convertsX-ray ionizing radiation into luminescent visible light. Thesemiconductor visible light detection subsystem has a quantum dotsemiconductor substrate and a plurality of quantum dot image sensors.The quantum dot image sensors detect the visible light from thescintillation subsystem and convert the visible light into at least oneelectronic signal. The scintillation subsystem is a plurality ofdiscrete scintillation packets, at least one of the discretescintillation packets communicating with at least one of the quantum dotimage sensors. A second preferred digital quantum dot radiographicdetection system may optionally have one or more of the followinginventive features: the plurality of quantum dot image sensors beingarranged in an array; the plurality of quantum dot image sensors beingheterogeneous; the plurality of discrete scintillation packets may beheterogeneous; an optically opaque layer being positioned betweendiscrete scintillation packets; an optically opaque lateral layer withoptical retroflectors positioned opposite the quantum dot image sensors.

The subject matter of the present invention is particularly pointed outand distinctly claimed in the concluding portion of this specification.However, both the organization and method of operation, together withfurther advantages and objects thereof, may best be understood byreference to the following descriptions taken in connection withaccompanying drawings wherein like reference characters refer to likeelements.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings illustrate various exemplary quantum dotdigital radiographic detection systems and/or provide teachings by whichthe various exemplary quantum dot radiographic detection systems aremore readily understood.

FIG. 1 is a graph showing the percentage quantum efficiency as afunction of visible wavelength of light of various conventional imagesensor arrays including CMOS and CCD visible light detectors.

FIG. 2 is a graph showing the percentage quantum efficiency as afunction of visible wavelength of light of various conventional imagesensor arrays including CMOS and CCD visible light detectors (as shownin FIG. 1) and, additionally, the wavelengths of two commonscintillation materials for converting ionizing x-radiation to visiblelight at the shown frequencies.

FIG. 3 is a graph similar to FIG. 2 showing, in addition, quantum dotdetector sensitivities of the tuned visible light ranges.

FIG. 4A is a simplified diagram showing the interaction betweenconventional image sensor arrays (including CCD or CMOS image sensors)and scintillation layers of conventional radiographic detection devices.

FIG. 4B is a simplified diagram showing exemplary interaction betweenquantum dot image sensor arrays and scintillation layers of exemplarypreferred quantum dot radiographic detection systems.

FIG. 5A is a simplified diagram showing the fields of view ofconventional image sensors with respect to the thickness ofscintillation layers of conventional radiographic detection devices.

FIG. 5B is a simplified diagram showing exemplary fields of view ofquantum dot image sensors with respect to the relative thickness ofscintillation layers of exemplary preferred quantum dot radiographicdetection systems.

FIG. 6A is a simplified diagram showing the placement of theconventional image sensors associated with the semiconductor substrateof conventional radiographic detection devices.

FIG. 6B is a simplified diagram showing exemplary placement of quantumdot image sensors associated with the semiconductor substrate ofexemplary preferred quantum dot radiographic detection systems.

FIG. 7A is a simplified diagram showing the placement of conventionalimage sensors associated with the semiconductor substrate, the field ofview of the image sensors with respect to the thickness of thescintillation layers, and the movement of scattered photons from thescintillation layers of conventional radiographic detection devices.

FIG. 7B is a simplified diagram showing exemplary placement of quantumdot image sensors associated with the semiconductor substrate, the fieldof view of the quantum dot image sensors with respect to the thicknessof the scintillation layers, and the movement of scattered photons fromthe scintillation layers of exemplary preferred quantum dot radiographicdetection systems.

FIG. 8A is a simplified diagram showing the density of conventionalimage sensor arrays (including CCD or CMOS image sensors) inconventional radiographic detection devices.

FIG. 8B is a simplified diagram showing exemplary density of quantum dotimage sensor arrays in exemplary preferred quantum dot radiographicdetection systems.

FIG. 9A is a simplified diagram showing density of conventional imagesensor arrays (including CCD or CMOS image sensors), the field of viewof conventional image sensors with respect to the thickness of thescintillation layers, and the movement of scattered photons from thescintillation layers in conventional radiographic detection devices.

FIG. 9B is a simplified diagram showing exemplary density of quantum dotimage sensor arrays, the field of view of quantum dot image sensors withrespect to the thickness of the scintillation layers, and the movementof scattered photons from the scintillation layers in exemplarypreferred quantum dot radiographic detection systems.

FIG. 10A is a simplified diagram showing placement of conventional imagesensors associated with the semiconductor substrate of conventionalradiographic detection devices.

FIG. 10B is a simplified diagram showing exemplary placement ofoptimized quantum dot image sensors associated with the semiconductorsubstrate of exemplary preferred quantum dot radiographic detectionsystems.

FIG. 11A is a simplified diagram showing conventional scintillationlayers, conventional image sensors, and conventional semiconductorsubstrates of conventional radiographic detection devices.

FIG. 11B is a simplified diagram showing quantum dot image sensors eachassociated with a discrete scintillation packet in exemplary preferredquantum dot radiographic detection systems.

FIG. 12A is a simplified diagram showing conventional radiographicdetection devices having optical “cross-talk” between conventional imagesensors, the conventional image sensors associated with conventionalscintillation layers.

FIG. 12B is a simplified diagram showing an exemplary preferred quantumdot radiographic detection system having reduced or eliminated optical“cross-talk” between quantum dot image sensors, each quantum dot imagesensor associated with a discrete scintillation packet.

FIG. 13A is a simplified diagram showing conventional radiographicdetection devices having optical “cross-talk” between conventional imagesensors, the conventional image sensors associated with conventionalscintillation layers.

FIG. 13B is a simplified diagram showing an exemplary preferred quantumdot radiographic detection system in which optical “cross-talk” betweenquantum dot image sensors is reduced or eliminated, each quantum dotimage sensor is associated with a discrete scintillation packet and anoptically opaque layer is positioned between the scintillation packets.

FIG. 14A is a simplified diagram showing conventional radiographicdetection devices having optical “cross-talk” between conventional imagesensors, the conventional image sensors associated with conventionalscintillation layers.

FIG. 14B is a simplified diagram showing an exemplary preferred quantumdot radiographic detection system in which optical “cross-talk” betweenquantum dot image sensors is reduced or eliminated, each quantum dotimage sensor associated with a discrete scintillation packet, anoptically opaque layer is positioned between the scintillation packets,and an optically opaque lateral layer with optical retroflectors ispositioned opposite the quantum dot image sensors.

The drawing figures are not necessarily to scale. Certain features orcomponents herein may be shown in somewhat schematic form and somedetails of conventional elements may not be shown or described in theinterest of clarity and conciseness. The drawing figures are herebyincorporated in and constitute a part of this specification.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein is a digital radiographic detection system and, morespecifically, a quantum dot digital radiographic detection system (alsoreferred to as a “quantum dot radiographic detector”). Exemplary quantumdot radiographic detection systems may be better understood withreference to the drawings, but the shown and described quantum dotradiographic detection systems are not intended to be of a limitingnature.

The exemplary quantum dot radiographic detection systems describedherein minimize most of the inherent limitations of CCD or CMOSconventional radiographic detection devices. For example, preferreddigital quantum dot radiographic detection systems have an image qualitysharp enough that edge detection software is not required, althoughadditional image enhancement will be possible. Further, preferreddigital quantum dot radiographic detection systems have higher contrastlevels than conventional digital radiographic detection devices becausethe image is not obfuscated by thick scintillation layers. The use ofpreferred digital quantum dot radiographic detection systems preferablyreduces patient X-ray exposure by approximately 25%-50% compared toconvention radiographic detection devices. Still further, preferredquantum dot radiographic detection systems have the ability to optimizequantum efficiencies to match multiple scintillation chemistries forenhanced X-ray detection. Finally, preferred digital quantum dotradiographic detection systems have the ability to capture parallelimages in real-time during single exposures to create the widest dynamicrange of any sensor in order to eliminate over and under exposed images.

Before describing the quantum dot digital radiographic detection system,some of the terminology should be clarified. Please note that the termsand phrases may have additional definitions and/or examples throughoutthe specification. Where otherwise not specifically defined, words,phrases, and acronyms are given their ordinary meaning in the art.

-   -   “Digital radiographic detection devices or systems” are used by        practitioners (i.e. any qualified user of radiographic detection        devices or systems) to perform the process of receiving a        radiation signal (such as X-rays), converting the radiation        signal into visible light (or “light”), detecting the light as a        plurality of images through the use of image sensors, converting        the plurality of images into corresponding electronic signals,        and digitally processing a plurality of electronic signals into        a single coherent image. It should be noted that “light” for the        purposes of this specification refers only to “visible light”        (i.e. light within the visible spectrum, but not X-rays or        infrared). In an exemplary quantum dot radiographic detection        system, X-rays are used to generate useful diagnostic images. In        order to produce these images, X-rays generated by an X-ray        source, pass through the patient's body and eventually into a        scintillation layer. The electrons in the scintillation material        are excited by the ionizing radiation (i.e. X-rays), and emit        visible light (by “luminescence”) based in the scintillating        material used. The visible light is then detected using the        semiconductor visible light detection subsystem and converted        into an electronic signal (similar to the process used in        digital photography). The efficiency of the semiconductor        visible light detection subsystem described herein may be        dependent on the semiconductor substrate and corresponding        circuitry used. The detected visible light can then be converted        into an electronic signal that is suitable for storage and        software manipulation to render the final diagnostic image.    -   “Quantum dot semiconductors” (also referred to as “quantum        dots,” “quantum dot detectors,” and “fluorescent semiconductor        nanocrystals”) are semiconductors whose excitations are confined        in all three spatial dimensions. As a result, the quantum dots        have properties that are between those of bulk semiconductors        and those of discrete molecules. The quantum dot radiographic        detection system described herein uses quantum dots in        combination with a scintillating medium to convert X-rays into        visible light and substantially concurrently capture the visible        light. Exemplary quantum dot semiconductors (quantum dot optical        devices with enhanced gain and sensitivity and methods of making        same) are described in U.S. Pat. No. 7,773,404 to Sargent et al.        (the “Sargent reference”), the disclosure of which is herein        incorporated by reference. On the other hand, U.S. Pat. No.        7,126,136 to Chen (the “Chen reference”) describes using        nanoparticles or quantum dots as exhibiting photostimulated        luminescence (“PSL”) for the storage of digital information. Put        another way, the quantum dots described herein function as        “detectors” whereas the quantum dots described in the Chen        reference function as optical emitters, which are the opposite        of detectors.

A “computational device,” “computing system,” “computer,” “processingunit,” and/or “processor” (referred to generically as “computationaldevices”) are devices capable of executing instructions or steps and maybe implemented as a programmable logic device or other type ofprogrammable apparatus known or yet to be discovered. The computationaldevices may have associated memory. A computational device may beimplemented as a single device or as a plurality of sub-devices.

The term “memory” is defined to include any type of computer (or othercomputational device)-readable media (also referred to asmachine-readable storage medium) including, but not limited to attachedstorage media (e.g. hard disk drives, network disk drives, servers),internal storage media (e.g. RAM, ROM, EPROM, FLASH-EPROM, or any othermemory chip or cartridge), removable storage media (e.g. CDs, DVDs,flash drives, memory cards, floppy disks, flexible disks), firmware,and/or other storage media known or yet to be discovered. Memory may beimplemented as a single device or as a plurality of sub-memories.

-   -   It should be noted that the terms “programs” and “subprograms”        are defined as a series of instructions that may be implemented        as “software” (i.e. computer program instructions or        computer-readable program code) that may be loaded onto a        computer (or other computational device) to produce a machine,        such that the instructions that execute on the computer create        structures for implementing the functions described herein.        Further, these programs and subprograms may be loaded onto a        computer so that they can direct the computer to function in a        particular manner, such that the instructions produce an article        of manufacture including instruction structures that implement        the functions described herein. The programs and subprograms may        also be loaded onto a computer to cause a series of operational        steps to be performed on or by the computer to produce a        computer implemented process such that the instructions that        execute on the computer provide steps for implementing the        functions described herein. The phrase “loaded onto a computer”        also includes being loaded into the memory of the computer or a        memory associated with or accessible by the computer. The        programs and subprograms may be divided into multiple modules or        may be combined.    -   It should be noted that the terms “may,” “might,” “can,” and        “could” are used to indicate alternatives and optional features        and only should be construed as a limitation if specifically        included in the claims. It should be noted that the various        components, features, steps, or embodiments thereof are all        “preferred” whether or not it is specifically indicated. Claims        not including a specific limitation should not be construed to        include that limitation.    -   It should be noted that, unless otherwise specified, the term        “or” is used in its nonexclusive form (e.g. “A or B” includes A,        B, A and B, or any combination thereof, but it would not have to        include all of these possibilities). It should be noted that,        unless otherwise specified, “and/or” is used similarly (e.g. “A        and/or B” includes A, B, A and B, or any combination thereof,        but it would not have to include all of these possibilities). It        should be noted that, unless otherwise specified, the terms        “includes” and “has” mean “comprises” (e.g. a device that        includes, has, or comprises A and B contains A and B, but        optionally may contain C or additional components other than A        and B). It should be noted that, unless otherwise specified, the        singular forms “a,” “an,” and “the” refer to one or more than        one, unless the context clearly dictates otherwise.

To perform the radiographic detection process, the exemplary digitalradiographic detection systems described herein utilize varioussubsystems. The subsystems of exemplary radiographic detection systemcan be discussed as the “scintillation subsystem” (which can be a“scintillation layer” or a “scintillation packet”), the “semiconductorvisible light detection subsystem,” and the “image processingsubsystem.”

Preferred scintillation subsystems convert X-ray ionizing radiation intoluminescent visible light. Conventional radiographic detection devicesuse scintillation layers made from a material suitable for convertingX-ray radiation into visible light (a “scintillation layer”), such as bythe use of a luminescent material. The luminescent material may be aconventional scintillation material (e.g. caesium iodine or gadoliniumoxysulfide), or may be phosphor materials as described in the Chenreference. Generally, scintillation layers are capable of producingadditional visible light in proportion to their thickness, but it isalso well known that as the scintillation layer gets thicker the imagebecomes “blurred” and image contrast decreases. Alternative preferredscintillation subsystems, as discussed below, may be implemented asdiscrete scintillation packets.

One preferred semiconductor visible light detection subsystem includes aplurality of image sensors (also referred to as “semiconductor visiblelight detectors” or “imagers”). Image sensors detect the light generatedby the scintillation subsystem and convert it into an electronic signalthrough the use of the semiconductor substrate. The semiconductorvisible light detection subsystem of the quantum dot digitalradiographic detection systems described herein includes quantum dotimage sensors in the semiconductor substrate (the quantum dotsemiconductor substrate). The semiconductor substrate includes thecircuitry and material necessary for converting the detected visiblelight signal into a corresponding electronic signal. Due to a limitedfield of view for each individual image sensor, a single image sensorwould be insufficient to capture an image of diagnostic value. Using anarray of image sensors associated with the semiconductor substratefacilitates the image sensors, in aggregate, having a field of viewsufficiently large enough to capture a useful diagnostic image (e.g. ofa patient's jaw).

One preferred image processing subsystem includes a computational device(e.g. a computer with an associated image rendering program) that iscapable of receiving electronic signals from the semiconductor visiblelight detection subsystem and digitally storing the electronic signalson an electronic medium as useful detection data. The computationaldevice then uses imaging software to align the electronic signals fromthe individual image sensors to create a larger diagnostic image. Theimage processing subsystem also includes any suitable connector betweenthe semiconductor visible light detection subsystem and the imageprocessing device.

FIGS. 1-3 are graphs pertaining to the scintillation subsystem and, inparticular, the at least one scintillation layer.

FIG. 1 is a graph showing the quantum efficiency (as a percentage (%QE)) of various conventional digital optical detection systems (such asCMOS or CCD detectors) as a function of wavelength of light. It shouldbe noted that although the % QE is very high at certain wavelengths, theluminescence of the scintillation material will generally control whatwavelength of visible light the image sensor will receive. FIG. 2 showsthe graph of FIG. 1 with the addition of the predominate wavelengths oftwo common scintillation materials: caesium iodide (460 nm) andgadolinium oxysulfide (622 nm). The graph shows the % QE at thesewavelengths for the various conventional digital radiographic detectionsystems to be between 25% and 65%. Because of the static nature of theconductivity properties of the semiconductors in these conventionalradiographic detection devices, the % QE cannot be improved at variouswavelengths without changing the semiconductor substrate.

In contrast to the semiconductor substrate of the conventional digitalradiographic detection system, a quantum dot semiconductor substrate canbe “attenuated” (have its conductivity properties adjusted) based on thesize and shape of the quantum dots. This allows for the production ofsemiconductor substrates that have high % QE at desirable wavelengths,such as the predominate wavelengths of the scintillation material. FIG.3 shows the graph of FIG. 1 with the addition of quantum dotradiographic detection systems (shown as dotted lines) havingsemiconductor substrates with quantum dots attenuated for caesium iodideand gadolinium oxysulfide luminescence. It should be noted that theattenuation is dynamic, and if a different scintillation material wasused, the quantum dot semiconductor substrate could be accordinglyattenuated for high % QE.

FIGS. 4-14 are each divided into “A” and “B” depictions. The A depictionrelates to conventional radiographic detection devices and the Bdepiction relates to quantum dot radiographic detection systems. Forsome features, multiple elements are only designated a single time. Forexample, an array of image sensors is designated by the same referencenumber as a single reference number.

FIG. 4A shows the interaction between conventional image sensor arrays(including CCD or CMOS image sensors 100) and scintillation layers 102of conventional radiographic detection devices. FIG. 4B shows exemplaryinteraction between quantum dot image sensor arrays (including quantumdot image sensors 200) and scintillation layers 202 of exemplarypreferred quantum dot radiographic detection systems. These figures showthat because quantum dot arrays 200 are able to detect four to ten timesmore available photons generated by the scintillation layer 202, thinnerscintillation layers 202 may be used with the quantum dot arrays 200.FIG. 4B shows exemplary scintillation subsystems and semiconductorvisible light detection subsystems of both conventional and quantum dotdigital radiographic detection systems. The scintillation layer 202 ofthe quantum dot digital radiography detection system is significantlythinner than the scintillation layers 102 of conventional digitalradiographic detection systems due to the increased ability of thesemiconductor visible light detection subsystem to detect photonsemitted by the scintillation subsystem. By altering the size and shapeof the quantum dots 200, the quantum dot radiographic detection systemcan detect between four and ten times as many free photons generated byconventional scintillation layers 102. This in turn requires lessvisible light from the scintillation layer 202 to generate a diagnosticimage, and therefore makes thicker conventional scintillation layers 102obsolete.

FIG. 5A shows the fields of view 104 of conventional image sensors 100with respect to the thickness of scintillation layers 102 ofconventional radiographic detection devices. FIG. 5B shows exemplaryfields of view 204 of quantum dot image sensors 200 with respect to thethickness of scintillation layers 202 of exemplary preferred quantum dotradiographic detection systems. These figures show an additional benefitto the quantum dot radiographic detection system's use of thinnerscintillation layers 202. In the conventional digital radiographicdetection systems, the conventional image sensors' fields of view 104are wide, causing significant overlap between image sensors 100 withinthe array. This overlap causes the resulting images to be less sharp(without the aid of expensive light collimation processes), andtherefore of less diagnostic value to a practitioner. In contrast, thequantum dot image sensors 200 of the quantum dot radiographic detectionsystem have much narrower fields of view 204. This narrow field of viewallows the image sensors 200 to be more densely positioned within thearray, resulting in both improved native image contrast and imagesharpness.

FIG. 6A shows the placement of the conventional image sensors 100 belowlayers of the semiconductor substrate 110 of conventional radiographicdetection devices. FIG. 6B shows exemplary placement of quantum dotimage sensors 200 above or on the top layer of the semiconductorsubstrate 210 of exemplary preferred quantum dot radiographic detectionsystems. FIG. 7A shows the placement of conventional image sensors 100associated with the semiconductor substrate 110, the field of view ofthe image sensors with respect to the thickness of the scintillationlayers 102, and the movement of scattered photons from the scintillationlayers 102 of conventional radiographic detection devices. FIG. 7B showsexemplary placement of quantum dot image sensors 200 associated with thesemiconductor substrate 210, the field of view of the quantum dot imagesensors with respect to the thickness of the scintillation layers 202,and the movement of scattered photons from the scintillation layers 202of exemplary preferred quantum dot radiographic detection systems. Asshown in these figures, the conventional image sensors 100 arepositioned significantly lower (shown as 5-8 layers into thesemiconductor substrate 110) as compared to quantum dot image sensors200 that are closer to or on the surface for “direct” contact withscintillation layers 202. It should be noted the term “direct” and thephrase “substantially direct” would not preclude the inclusion of anadhesive or other de minimus attachment layer or gap between the quantumdot image sensors 200 and the scintillation layers 202. Because theconventional image sensors 100 of conventional radiographic detectiondevices are located below several layers of the semiconductor substrate110, there is an undesirably large distance between the scintillationlayer 102 and the image sensors 100. This distance can lead to lostphotons due to spatial defocusing, scattering, and absorption by thesemiconductor substrate 110. In contrast, the quantum dot radiographicdetection system allows the quantum dot image sensors 200 to bepositioned in direct contact with (or substantially close to) thesurface of the scintillation layer 202. This positioning allows thepractitioner to obtain a superior quality image by eliminating orminimizing the loss of photons from the interference of thesemiconductor substrate 210.

FIG. 8A shows the density of conventional image sensor arrays (includingCCD or CMOS image sensors 100) in conventional radiographic detectiondevices. FIG. 8B shows exemplary density of quantum dot image sensorarrays (including quantum dot image sensors 200) in exemplary preferredquantum dot radiographic detection systems. FIG. 9A shows density ofconventional image sensor arrays (including CCD or CMOS image sensors100), the field of view of conventional image sensors with respect tothe thickness of the scintillation layers 102, and the movement ofscattered photons from the scintillation layers 102 in conventionalradiographic detection devices. FIG. 9B shows exemplary density ofquantum dot image sensor arrays (including quantum dot image sensors200), the field of view of quantum dot image sensors with respect to thethickness of the scintillation layers 202, and the movement of scatteredphotons from the scintillation layers 202 in exemplary preferred quantumdot radiographic detection systems. These figures show the relative sizelimitations of both the conventional and quantum dot radiographicdetection systems. In the conventional radiographic detection devices,the combination of the thick scintillation layer 102 and the position ofthe image sensors 100 below layers of the semiconductor substrate 110significantly contribute to the image sensors' wide field of view 104(FIG. 9A). These inherent qualities of the conventional radiographicdetection devices makes increasing the density of image sensor array 100impracticable, as it would simply increase the field of view overlap. Incontrast, FIG. 9B shows that quantum dot radiographic detection systemsare inherently capable of having a higher image sensor array densitywithout causing the image sensors' fields of view 204 to overlap. Higherdetector densities results in dramatically higher native image contrastand resolution along with the ability to detect more photons.

As shown in FIGS. 1-3, conventional image sensors 100 have a broadbandresponse, but not high quantum efficiency. The various scintillationchemistries have a narrow band output. Quantum dot image sensors 200 canbe tuned (e.g. optimized) to the peak outputs of these scintillationchemistries. Comparing FIG. 10A with FIG. 10B shows the advantage ofthis ability to tune/optimize the quantum dot image sensors 200. FIG.10A shows placement of conventional image sensors 100 having nonlinearbroadband frequency responses. FIG. 10B shows exemplary placement ofoptimized quantum dot image sensors 200′ associated with thesemiconductor substrate 210 of exemplary preferred quantum dotradiographic detection systems. The optimized quantum dot image sensors200′ are preferably tuned to the peak output of the scintillation layer202. Optimization permits the specific scintillation chemistry to beused for greater conversion of available photons into useable data.

FIG. 11A shows conventional scintillation layers 102, conventional imagesensors 100, and conventional semiconductor substrates 110 ofconventional radiographic detection devices. FIG. 11B shows quantum dotimage sensors 200 (shown as 200 a, 200 b) each associated with adiscrete scintillation packet 212 (shown as 212 a, 212 b) in exemplarypreferred quantum dot radiographic detection systems. In thisalternative quantum dot radiographic detection system, the scintillationsubsystem includes discrete scintillation packets 212 instead of anoverlying scintillation layer 102. These figures show individualscintillation packets 212 associated with individual quantum dot imagesensors 200 on a one-to-one basis, although alternative scintillationpacket-to-image sensor ratios may be used. The use of separatedscintillation packets 212 in lieu of a uniform scintillation layer 102allows the quantum dot radiographic detection system to be furtherattenuated by the use of more than one scintillation material. Forexample, the array of quantum dot image sensors 200 optionally may beheterogeneous (shown graphically as 200 a, 200 b) with respect to theoptimum % QE, with 50% of the image sensors 200 a being attenuated formaximum quantum efficiency at 460 nm, and 50% of the image sensors 200 bbeing attenuated for maximum quantum efficiency at 622 nm. Thescintillation packets 212 (shown graphically as 212 a, 212 b) may besimilarly heterogeneous and associated with the appropriate (designedtogether to provide the correct results) quantum dot image sensors 200a, 200 b based on the scintillation material, having caesium iodidescintillation packets 212 a associated with the 460 nm image sensors 200a, and having the gadolinium oxysulfide scintillation packets 212 bassociated with the 622 nm image sensors 200 b. The resulting images arederived from two separate scintillation materials, and the resultingimages have higher resolution and contrast, resulting in greaterdiagnostic value.

FIGS. 12A and 13A show conventional radiographic detection deviceshaving optical “cross-talk” between conventional image sensors 100, theconventional image sensors 100 associated with conventionalscintillation layers 102. FIG. 12B shows an exemplary preferred quantumdot radiographic detection system having optical “cross-talk” betweenquantum dot image sensors 200, each quantum dot image sensor 200associated with a discrete scintillation packet 212. Optical“cross-talk” in the scintillation layer loses photons and diminishesimage contrast and sharpness as viewed by the optical detectors. Asshown in FIG. 13A, optical “cross-talk” between conventional imagesensors 100 cannot be eliminated because of the presence of theconventional scintillation layer 102. On the other hand, FIG. 13B showsan exemplary preferred quantum dot radiographic detection system inwhich optical “cross-talk” between quantum dot image sensors 200 isreduced or eliminated by adding an optically opaque layer 220 positionedbetween the scintillation packets 212.

FIG. 14A shows conventional radiographic detection devices havingoptical “cross-talk” between conventional image sensors 100, theconventional image sensors 100 associated with conventionalscintillation layers 102. FIG. 14B shows an exemplary preferred quantumdot radiographic detection system in which optical “cross-talk” betweenquantum dot image sensors 200 is reduced or eliminated using anoptically opaque layer 220 positioned between the scintillation packets212. FIG. 14B also shows the use of an optically opaque lateral layer220 with optical retroflectors 230 positioned opposite the quantum dotimage sensors 200. Put another way, the scintillation packets 212 aresandwiched between the opaque lateral layer 220 with opticalretroflectors 230 and the quantum dot image sensors 200. The opticallyopaque lateral layer 220 with optical retroflectors 230 increasesoptical gain by reflecting scattered photons toward the quantum dotimage sensors 200.

Alternative embodiments incorporating various elements described aboveare contemplated. For example, although shown as having heterogeneousquantum dot image sensors 200 a, 200 b, homogeneous quantum dot imagesensors 200 could be used in the embodiments of FIGS. 11B, 12B, 13B,and/or 14B. Another example is that the optically opaque lateral layer220 with optical retroflectors 230 shown in FIG. 14B could be usedwithout the optically opaque layer positioned between the scintillationpackets 212. A single discrete scintillation packet 212 may communicatewith a plurality of quantum dot image sensors 200. A plurality ofdiscrete scintillation packets 212 may communicate with a single quantumdot image sensor 200.

Cross-talk eliminating systems that eliminate optical cross-talk betweenimage sensors and scintillation layers in conventional radiographicdetection devices can also be used with the quantum dot radiographicdetection systems described above. These conventional cross-talkeliminating systems generally consist of a collimated plate consistingof aligned fiber optics (having fibers that are glued, cut, andpolished). Problems with conventional cross-talk eliminating systemsinclude, but are not limited to their thickness, their delicateness, andtheir expensiveness. Accordingly, systems such as those described abovethat eliminate cross-talk in other ways would be extremely valuable.

It is to be understood that the inventions, examples, and embodimentsdescribed herein are not limited to particularly exemplified materials,methods, and/or structures. Further, all foreign and/or domesticpublications, patents, and patent applications cited herein, whethersupra or infra, are hereby incorporated by reference in their entirety.

The terms and expressions that have been employed in the foregoingspecification are used as terms of description and not of limitation,and are not intended to exclude equivalents of the features shown anddescribed. While the above is a complete description of selectedembodiments of the present invention, it is possible to practice theinvention using various alternatives, modifications, adaptations,variations, and/or combinations and their equivalents. It will beappreciated by those of ordinary skill in the art that any arrangementthat is calculated to achieve the same purpose may be substituted forthe specific embodiment shown. It is also to be understood that thefollowing claims are intended to cover all of the generic and specificfeatures of the invention herein described and all statements of thescope of the invention which, as a matter of language, might be said tofall therebetween.

What is claimed is:
 1. A digital quantum dot radiographic detectionsystem comprising: (a) a scintillation subsystem that converts X-rayionizing radiation into luminescent visible light; (b) a semiconductorvisible light detection subsystem having a semiconductor substrate and aplurality of quantum dot image sensors, said quantum dot image sensorsdetecting said visible light from said scintillation subsystem andconverting said visible light into at least one electronic signal; and(c) said plurality of quantum dot image sensors is in substantiallydirect contact with said scintillation subsystem.
 2. The system of claim1 wherein said plurality of quantum dot image sensors are arranged in anarray.
 3. The system of claim 1 wherein said plurality of quantum dotimage sensors are heterogeneous.
 4. The system of claim 1 wherein saidscintillation subsystem comprises a plurality of discrete scintillationpackets, at least one of said discrete scintillation packetscommunicating with at least one of said quantum dot image sensors. 5.The system of claim 1 wherein said scintillation subsystem comprises aplurality of discrete scintillation packets, said plurality of quantumdot image sensors and said plurality of discrete scintillation packetsbeing heterogeneous, at least one of said discrete scintillation packetscommunicating with an appropriate at least one of said quantum dot imagesensors.
 6. The system of claim 1 wherein said scintillation subsystemcomprises a plurality of discrete scintillation packets, at least one ofsaid discrete scintillation packets communicating with at least one ofsaid quantum dot image sensors, and an optically opaque layer beingpositioned between said discrete scintillation packets.
 7. The system ofclaim 1 wherein said scintillation subsystem comprises a plurality ofdiscrete scintillation packets, said plurality of quantum dot imagesensors and said plurality of discrete scintillation packets beingheterogeneous, at least one of said discrete scintillation packetscommunicating with an appropriate at least one of said quantum dot imagesensors, and an optically opaque layer being positioned between saiddiscrete scintillation packets.
 8. The system of claim 1 wherein saidscintillation subsystem comprises a plurality of discrete scintillationpackets, at least one of said discrete scintillation packetscommunicating with at least one of said quantum dot image sensors, andan optically opaque lateral layer with optical retroflectors positionedopposite said quantum dot image sensors.
 9. The system of claim 1wherein said scintillation subsystem comprises a plurality of discretescintillation packets, said plurality of quantum dot image sensors andsaid plurality of discrete scintillation packets being heterogeneous, atleast one of said discrete scintillation packets communicating with anappropriate at least one of said quantum dot image sensors, and anoptically opaque lateral layer with optical retroflectors positionedopposite said quantum dot image sensors.
 10. The system of claim 1wherein said scintillation subsystem comprises a plurality of discretescintillation packets, at least one of said discrete scintillationpackets communicating with at least one of said quantum dot imagesensors, an optically opaque layer being positioned between saiddiscrete scintillation packets, and an optically opaque lateral layerwith optical retroflectors positioned opposite said quantum dot imagesensors.
 11. The system of claim 1 wherein said scintillation subsystemcomprises a plurality of discrete scintillation packets, said pluralityof quantum dot image sensors and said plurality of discretescintillation packets being heterogeneous, at least one of said discretescintillation packets communicating with an appropriate at least one ofsaid quantum dot image sensors, an optically opaque layer beingpositioned between said discrete scintillation packets, and an opticallyopaque lateral layer with optical retroflectors positioned opposite saidquantum dot image sensors.
 12. The system of claim 1 wherein saidscintillation subsystem is positioned between an X-ray source and saidplurality of quantum dot image sensors.
 13. The system of claim 1further comprising: (a) an image processing subsystem having acomputational device capable of receiving said at least one electronicsignal and storing said at least one electronic signal on an electronicmedium; and (b) said computational device capable of retrieving anddisplaying said at least one electronic signal at a concurrent or latertime as a diagnostic image.
 14. A digital quantum dot radiographicdetection system comprising: (a) a scintillation subsystem that convertsX-ray ionizing radiation into luminescent visible light; (b) asemiconductor visible light detection subsystem having a semiconductorsubstrate and a plurality of quantum dot image sensors, said quantum dotimage sensors detecting said visible light from said scintillationsubsystem and converting said visible light into at least one electronicsignal; and (c) said scintillation subsystem being a plurality ofdiscrete scintillation packets, at least one of said discretescintillation packets communicating with at least one of said quantumdot image sensors.
 15. The system of claim 14 wherein said plurality ofquantum dot image sensors are arranged in an array.
 16. The system ofclaim 14 wherein said plurality of quantum dot image sensors areheterogeneous.
 17. The system of claim 14 wherein said plurality ofquantum dot image sensors and said plurality of discrete scintillationpackets are heterogeneous, at least one of said discrete scintillationpackets communicating with an appropriate at least one of said quantumdot image sensors.
 18. The system of claim 14 further comprising anoptically opaque layer being positioned between said discretescintillation packets.
 19. The system of claim 14 further comprising anoptically opaque lateral layer with optical retroflectors positionedopposite said quantum dot image sensors.
 20. The system of claim 14further comprising an optically opaque layer being positioned betweensaid discrete scintillation packets and an optically opaque laterallayer with optical retroflectors positioned opposite said quantum dotimage sensors.
 21. The system of claim 1 wherein said semiconductorsubstrate is a quantum dot semiconductor substrate.
 22. The system ofclaim 14 wherein said semiconductor substrate is a quantum dotsemiconductor substrate.
 23. The system of claim 1 wherein saidplurality of quantum dot image sensors are heterogeneous in that thereare a plurality of different types of quantum dot image sensors.
 24. Thesystem of claim 1, said scintillation subsystem comprising a pluralityof discrete scintillation packets, at least one of said discretescintillation packets being in substantially direct contact with and incommunication with an associated at least one of said quantum dot imagesensors.
 25. The system of claim 1, said scintillation subsystemcomprising a plurality of discrete scintillation packets, at least oneof said discrete scintillation packets in substantially direct contactwith and in communication with an associated at least one of saidquantum dot image sensors, each said quantum dot image sensor beingoptimized to a peak output of a scintillation chemistry of itsassociated discrete scintillation packet.
 26. The system of claim 1,said scintillation subsystem comprising a plurality of discretescintillation packets, at least one of said discrete scintillationpackets in substantially direct contact with and in communication withan associated at least one of said quantum dot image sensors, each saidquantum dot image sensor being optimized to a peak output of ascintillation chemistry of its associated discrete scintillation packet,wherein different types of optimized quantum dot image sensor andassociated discrete scintillation packet combinations provide imageshaving a high resolution and contrast.
 27. The system of claim 14wherein said plurality of quantum dot image sensors are heterogeneous inthat there are a plurality of different types of quantum dot imagesensors.
 28. The system of claim 14, at least one of said discretescintillation packets being in substantially direct contact with and incommunication with an associated at least one of said quantum dot imagesensors.
 29. The system of claim 14, each said quantum dot image sensorbeing optimized to a peak output of a scintillation chemistry of itsassociated discrete scintillation packet.
 30. The system of claim 14,each said quantum dot image sensor being optimized to a peak output of ascintillation chemistry of its associated discrete scintillation packet,wherein different types of optimized quantum dot image sensor andassociated discrete scintillation packet combinations provide imageshaving a high resolution and contrast.
 31. A digital quantum dotradiographic detection system comprising: (a) a scintillation subsystemthat converts X-ray ionizing radiation into luminescent visible light;(b) a semiconductor visible light detection subsystem having asemiconductor substrate and a plurality of quantum dot image sensors,said quantum dot image sensors detecting said visible light from saidscintillation subsystem and converting said visible light into at leastone electronic signal; and (c) said scintillation subsystem being aplurality of discrete scintillation packets, at least one of saiddiscrete scintillation packets in substantially direct contact with andcommunicating with at least one of said quantum dot image sensors, eachsaid quantum dot image sensor being optimized to a peak output of ascintillation chemistry of its associated discrete scintillation packet.